Everton will be without their first-choice goalkeeper, Tim Howard, for several weeks after he broke two bones in his back during the FA Cup win over Oldham Athletic.

Howard sustained the injury in the 85th minute of Everton's fifth-round replay victory when he landed awkwardly after a foul by the Oldham striker, Robbie Simpson. The 34-year-old played out the final five minutes plus three minutes of stoppage time with the broken bones, making several saves as Everton held out for the 3-1 win that secured Saturday's quarter-final against Wigan Athletic.

The US international is expected to feature again this season and will not require surgery. His injury is similar to that suffered by Fabricio Coloccini last month when the Newcastle captain made an overhead clearance against Southampton. Coloccini's time out has been estimated at "three to seven weeks" by his manager, Alan Pardew.

David Moyes, the Everton manager, said: "Tim is out against Wigan. He has broken two bones in his back. We don't think he will be out for the season. I read that Coloccini could be out for seven weeks but we are not sure how long Tim will be out for because, obviously with a goalkeeper, he has to dive around and hit the ground.

"I have let him go away for a few days. It might be that, if everything goes well, he misses next week's game as well [against Manchester City] and then because of the international break he might be close after the rest because that would be four weeks.

"He has two fractures, but they are not bones that are supporting anything. It is off the spine. They are not weight-bearing. It just needs a bit of healing time. It is not like a pure fracture where you need to wait to look at it. It is a question of whether he can cope with the pain. The bones will heal themselves but it's not good."

Jan Mucha replaced Howard for the Premier League defeat of Reading last Saturday and will make his FA Cup debut against Wigan. The Slovakia international has made only eight appearances for Everton since arriving on a free transfer from Legia Warsaw almost three years ago. Everton cannot make an emergency loan signing for the FA Cup but will consider options for the Premier League. Their substitute keeper for the quarter-final is 19-year-old Mason Springthorpe, a £125,000 signing from Shrewsbury Town in February 2011.

Moyes remains aggrieved at the treatment, and lack of protection, that Howard received against Oldham. Simpson was booked for his challenge on the Everton keeper and Moyes said: "He [Howard] did incredibly well to finish the Oldham game. I thought he [Simpson] took him out when the goalkeeper jumped for the ball. He went under him. When Tim fell he tipped over him like a tree."

Everton's defensive problems for the quarter-final are not limited to goalkeeper. Phil Jagielka is also absent having undergone surgery after the Reading game to stitch up a gashed leg. The England international will be out for approximately three weeks, making him a major doubt for the World Cup qualifiers against San Marino and Montenegro late this month.

Jagielka's likely replacement against Wigan, John Heitinga, endured a miserable afternoon earlier in the season against Roberto Martínez's team – and particularly Arouna Koné. But Moyes, who replaced the Dutch international at half-time at the DW Stadium in October, insists he has no concerns over a repeat performance.

"Johnny Heitinga has got massive experience," said the Everton manager. "His knowledge and understanding of the game is excellent, he has played at the highest level throughout his career. We are talking about a very experienced player. He started the season very well and he is a really confident player, which is something that really helps. Johnny will be able to handle it. He can handle most things. Very little bothers him. He can brush things off quickly and move on."

Moyes admits Everton's third quarter-final in five seasons represents "a defining game" in the club's season but is keen to guard against complacency at Goodison Park. "People are saying it would be great to get to Wembley again but the next game is not the final and we have to beat Wigan first," Moyes said.

"Roberto has said he will make changes but my mind says Wigan will play their best team. I do understand Roberto's position because if you gave him a choice now of the FA Cup final or finishing fourth from bottom of the Premier League, I've no doubt what he would take. But you can separate the competitions at times.

"Similarly, if I was offered a choice now of the FA Cup final or Champions League qualification, I know what I'd take. The Champions League would offer the finances to transform the club."